Type ACE97
12
are shown in Table 2. In order to evaluate a valve,
examine the valve nameplate to determine the C
v
and
inlet pressure range (main valve spring).
There are four pressures involved in evaluating a
valve: actual inlet pressure, pressure to start opening
pilot valve, pressure to start opening main valve, and
pressure to fully open main valve.
Actual Inlet Pressure: The gas pressure supplied
to the inlet of the valve. This is the maximum
diagnostic pressure.
Pressure to Start Opening Pilot Valve: The
diagnostic pressure drops to this value as the valve
senses decreasing tank pressure. The main pad
valve remains closed at this pressure.
Pressure to Start Opening Main Valve: The
diagnostic pressure drops to this level as the tank
pressure decreases the valve setpoint. The pilot is
fully open at this pressure.
Pressure to Fully Open Main Valve: At this point,
both the main valve and pilot valve are fully open
and supplying gas to the tank.
Follow these steps and refer to the diagnostics tables
(Tables 3 through 11) to evaluate a valve under actual
operating conditions:
1. Select the table (Tables 3 through 11) that
corresponds to the C
v
and inlet pressure range
of your pad valve.
2. Determine the actual valve operating inlet pressure
in the rst column of the diagnostics table.
3. In the second column of the table, determine the
pressure of the pilot as it opens.
4. Determine the diagnostic pressure for the start to
open pressure of the main valve in the third column.
5. The fourth column displays the diagnostic pressure
for the full open pressure of the main valve.
Disassembly and Assembly
CAUTION
Before removing the valve from the line,
ensure that it is isolated from the gas
supply pressure and that all pressure
has been released from the valve. All
tank connections must be closed or
sealed in accordance with your plant’s
operating and safety procedures.
If installed, electrical connections
to the explosion proof switch must
be deactivated before opening the
enclosure or disconnecting the
wiring (in accordance with codes
and safety practices).
Refer to the following instructions and to Figures 11
through 20 in the Parts Ordering section when
performing assembly and disassembly operations.
It is recommended that all seals and diaphragms be
replaced whenever a valve is disassembled and
re-assembled. Parts kits are available through your
local Sales Ofce.
Note
Have your model number, serial number,
inlet pressure, and set pressure range
available when ordering parts. Valve
information is on the nameplate (on the
upper actuator case).
The Type ACE97 Pad-Depad valve should be viewed
as four connected elements. These include the pad
valve, the actuator, the depad pilot valve, and the
depad main valve. See Figure 1.
Disassembly
When performing disassembly operations, please take
care not to adjust or alter the pressure setpoints. Read
the following instructions carefully before proceeding.
Depad Pilot Valve Removal
Refer to Figures 11 and 19.
1. Disconnect the tubing lines (key 143, three
connections) from the depad pilot valve.
2. Loosen the locknut (key 99) but maintain its
position in relation to the adjusting coupling
(key 107). By maintaining the position of the
locknut and the lower cage (key 110), the depad
setpoint remains unchanged.
3. Separate the pilot valve from the spring case
(key 120) by unthreading and removing.
Depad Pilot Valve Disassembly
Refer to Figure 19.
1. Unthread and remove the coupling (key 107).
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